Fructooligosaccharides are a mixture of oligosaccharides including 1-Kestose (GF2), Nystose (GF3) and Fructosyl nystose (GF4), in which 1 to 3 molecule(s) of fructose are bound to sucrose by ®-(2,1) linkage, respectively and are widely contained in plants such as asparagus, onion, potato, honey, etc. They are currently spotlighted as food materials, together with oligosaccharides, due to their outstanding functions, including for example, low caloric value, promotion of proliferation of lactic acid bacteria and bifidobacteria, improvement of microflora in the intestines and inhibition of growth of pathogenic bacteria, improvement of bowel movement, and strengthening of immunity. Thus, examples of applications of oligosaccharides can be found in various industrial fields, including food, drink, confectionery, health food, and the like.
Particularly, it has been reported that the fructooligosaccharides showed excellent calcium-absorption effect when used in combination with difructose anhydride III (DFA III) (See, Japanese Patent Publication No. 11-43438). U.S. Pat. No. 5,827,526 disclosed that the duration and recurrence of diarrhea in a human can be reduced when 0.5 grams to 5 grams of fructooligosaccharides per day is administered to the patient.
Korean Patent Application Laid-Open No. 2000-57520 disclosed that a mixture of fructooligosaccharides and galactooligosaccharides with various edible ingredients may improve the flow in the bowel and effectively express prebiotic effects, as compared to other oligosaccharides. Also, currently, fructooligosaccharides are subjects of research and studies to develop diets for diabetic patients, since they are excellent in improvement of bowel movement by inducing proliferation of lactobacillus bifidus, one of the bacteria comprising normal microflora of human bowels, do not affect blood sugar levels upon ingestion, and are not decomposed by any digestive enzyme. Further, they are shown to reduce cholesterol levels in the blood and liver. Therefore, such effects of fructooligosaccharides now are not receiving careful study.
Conventionally, fructooligosaccharides have been produced by methods using microorganisms which can prepare fructosyl transferase. There are known for example, a method using the Aureobasidium pullulans strain, a method using Aspergillus niger and a method using strains of Penicillium and Fusarium sps. However, fructosyl transferase prepared by these methods has a disadvantage of a low sucrose hydrolysis titer.
Japanese Unexamined Patent Application No. 10-165192 disclosed a method for preparing ®-fructofuranosidase using Penicillium citrinum FERM P-15944 fungus, by which a mixture of conventional fructooligosaccharides with neofructooligosaccharides could be produced from sucrose. It is described that the neofructooligosaccharides is a mixture consisting of neokestose (6G-®-fructofuranosyl-sucrose), neonystose (6G-®-fructofuranosyl-kestose) and neofructosyl nystose (6G-®-fructofuranosyl-nystose), which have a structure in which 1 to 3 molecule(s) of fructose is (are) bound to sucrose by ®-(2,6) linkage, respectively, different from conventional fructooligosaccharides. It is also described that neofructooligosaccharides have moisturizing effects, excellent sweetness, low calories and anti-cavity effects, functions to induce proliferation of bacteria in the bowels and to promote topical immune responses in the intestinal tracts, and thus can be applicable in various fields such as sweeteners, functional foods, feed stuffs, medicines, and promoters of pesticides.
D. Grizard et al. disclosed a method for producing a mixture of fructooligosaccharides and neofructooligosaccharides using Cytolase PCL5, a commercially available enzyme derived from Aspergillus awamori (D. Grizard, C. Barthomuf, Food Biotechnology, 13 (1), 93-105, 1999).
U.S. Pat. No. 5,334,516 disclosed a method for producing neofructooligosaccharides (expressed as “branched fructooligosaccharides”) with conventional fructooligosaccharides using an enzyme derived from Aspergillus sydowi. 
Thus, the present inventors have intensively investigated and studied the prior arts and have conducted research in various ways to produce fructooligosaccharides in a high yield. As a result, we have finally identified a novel microorganism which is capable of producing fructosyl transferase having a high sucrose hydrolysis titer and confirmed that conventional fructooligosaccharides and neofructooligosaccharides could be produced in a high yield via a reaction of the microorganism with a highly concentrated sucrose solution. Based on these discoveries, the present invention has been developed.